Calculating Boost

M

mdaj

Member

:

car

• Nov 6, 2003

• #1

Quick question:

If I am correct the 2.0L FSDE has 121.4 CID (which should be same for Mazdaspeed).

I am trying to figure out bhp/cid. When doing so will I be going for the power to the ground or at the crank?

If ground then this is my calc: .060bhp/cid * 121.4cid * (boost +14.7ap)= 150 which is the power to the ground for MSP's.

If crank then its .068bhp/cid for 170hp.

BTW- I am reading Corkey Bell thats where I got the calcs from.

 

Last edited: Nov 6, 2003

L

LinuxRacr

Contributor

:

2001 Mazda MP3

• Nov 7, 2003

• #2

Wow! Amazing! I'll have to look that up in my copy of Maximum Boost.

 

I

igdrasil

:

12psi Protege5

• Nov 7, 2003

• #3

i dont see that equation correct they way its expressed there:

0.060/cid * 121.4 will cancel 121.4 in both?

 

K

Kooldino

MOTM Winner Jan '09

Authorized Vendor

Contributor

:

MP3

• Nov 7, 2003

• #4

Wait..you're trying to find how much HP per cid? IF so, then why is air pressure part of the equation?

 

M

mdaj

Member

:

car

• Nov 7, 2003

• #5

Not so much as hp per cid but overall HP. I would think the atmospheric pressure at sea-level would need to be included when calculating estimated hp. Although, I don't know much about cars technically.

The formula is set-up in Corky's book. I have read it twice but have a bad memory so I cant really answer your question igdrasil. I believe in my line of thinking that it will need to used to find overall CID HP Displacement and then multiplying by your sea level AP.

I don't know...my brain hurts

 

J

jred321

:

GLA45

• Nov 7, 2003

• #6

what page is the equation on?

 

M

mdaj

Member

:

car

• Nov 7, 2003

• #7

Page 12 under "And Furthermore". I need to reread everything and maybe now that I have a turbo I will pay more attention to what everything says.

 

J

jred321

:

GLA45

• Nov 7, 2003

• #8

so what are you actually trying to figure out?
either way, you'll need to know bhp and the boost your car is actually running. bhp will be slightly higher than whp due to the car not having to spin the wheels, you need a dyno that you take your wheels off and spin it to measure this. if you assume bhp is say 155, and let's say boost is 6psi, then bhp/cid=0.06168.
but i don't get really what this number helps, it's just an efficiency rating of the motor.

 

M

mdaj

Member

:

car

• Nov 7, 2003

• #9

I just wanted to know if it was measured by wheel (brake) or crank. I was plugging in some numbers to view power output at different boost levels as an estimate. But thanks for your help.

 

J

jersey_emt

Member

:

04 MSM #1089

• Nov 7, 2003

• #10

mdaj said:

I just wanted to know if it was measured by wheel (brake) or crank. I was plugging in some numbers to view power output at different boost levels as an estimate. But thanks for your help.

Click to expand...

Yeah, I played around with that equation as well. I figured out the bhp for several levels (6.5, 8.5, and 10psi)...it's all written in the margin of the book.

Problem is, the book's in my car right now, and I don't feel like walking outside.

 

M

mdaj

Member

:

car

• Nov 8, 2003

• #11

Yeah, I have stickey notes all on my page for different boost levels